Reference may be made to the article “A portable single-basin solar still with an external reflecting booster and an outside condenser” published in Desalination 280 (2011) 332-338, by Monowe et. al, which describes design of a portable thermal-electrical solar still with an external reflecting booster and an outside condenser. The main aim of the paper is to recover the heat from condensation of vapors. The approach is less relevant to Indian climatic conditions, especially during summer months, besides the fact that electrical energy is also required to operate a fan connected to the condenser.
Reference may be made to a paper by Velmurugan et. al. entitled “Productivity enhancement of stepped solar still-Performance analysis”, published in Thermal Science Vol. 12 (2008), No. 3, pp. 153-163, where theoretical and experimental analysis were made for fin type, sponge type, and combination of fin and sponge type stepped solar still.
Reference may be made to a paper by Shanmugan et. al. entitled “Performance study on an acrylic mirror boosted solar distillation unit utilizing seawater”, published in Desalination 230 (2008) 281-287, where the performance of solar still in terms of collection of distilled water have been analyzed and a booster mirror (acrylic) is attached with just above the glass cover of solar still. The reported result with this boosted distillation unit was 4.2 L/m2/d at 890 W/m2 max.
Reference may be made to an article, “Monthly optimum inclination of glass cover and external reflector of a basin type solar still with internal and external reflector” published in Solar Energy 84(2010) 1959-1966, which reports a theoretical analysis of a basin type solar still with internal and external reflectors. Theoretically predicted distillate produced by the still throughout the year, varies according to the inclination angle of both the glass cover and the external reflector. No experimental work has been carried out in this paper.
Reference may be made to US 7008515B1 dated Mar. 7, 2006 wherein a solar still is described with improved enclosure and evaporation assembly. The evaporation assembly floats on a body of source water and is readily collapsed and folded for storage or transport. The enclosure assembly includes a transparent conical dome covering a collection reservoir and an inner float ring. The evaporation assembly is placed in the center of the inner float ring. During operation, solar radiation causes water to evaporate from the evaporation assembly. The water vapor is then condensed and collected by the enclosure assembly. No mention is made to the use of improved condenser assembly for enhancement of daily productivity.
Reference may be made to Indian Patent Application No. 1550/DEL/2009 dated 27th July by Maiti et al. wherein PV panel assemblies having high aspect ratio are fitted with N-S reflectors in V-trough to raise the insolation on the panel and, consequently, the derived electrical power. No mention is made therein of the use of such reflector assemblies on the solar still.
Reference may be made to U.S. Pat. No. 5,053,110A dated Oct. 1, 1991 wherein a solar still described consists of an evaporating collector dome which is provided with a smooth interior surface to permit collection of distillate. The apparatus exterior is provided with a black surface to serve as a black body and so absorb increased amounts of the sun's energy. Additionally, that same exterior is coated with a film of infra-red absorbing material to further increase solar-energy absorption. To further improve the system's efficiency, various external tubing designs are utilized to preheat the load prior to its entry into the evaporating chamber. The invention does not mention the presence of condensers to enhance condensation efficiency.
Reference may be made to U.S. Pat. No. 4,406,749A dated Sep. 27, 1983 wherein a solar still is described in which the water to be distilled is confined within an internal chamber and subjected to solar energy through a transparent lid. The water that is distilled collects on the interior surface of the lid. The lid is located at an inclined position with respect to gravity. The droplets of distilled water which adhere to the interior surface of the lid flow to the lowest elevation of the lid. These accumulated droplets of distilled water are to be removed and collected within a collecting container. A water inlet valve assembly is connected to supply water within the internal chamber. No mention is made to the use of side condensers and north-south reflectors for enhancement of daily productivity.
Reference may be made to a paper by F. F. Tabrizi et al. entitled “Effect of water flow rate on internal heat and mass transfer and daily productivity of a weir-type cascade solar still” published in Desalination 260(2010) 239-247 which reports the construction of a cascade solar still (CSS) designed for water purification with a view of enhancing the daily productivity. The results showed a decrease in the internal heat and mass transfer rates as well as daily productivity with an increase in water flow rate. No mention is made to the use of side condensers for enhancement of daily productivity.
Reference may be made to the work by H. S. Kwatra in the article, “Performance of a solar still: Predicted effect of enhanced evaporation area on yield and evaporation temperature” published in Solar Energy 56(1996) 261-266. The work describes a solar still with enlarged evaporation area and computer simulation in order to explore the quantitative relationship between evaporation area and the distillation yield. The article does not report any experimental study.
Reference may be made to a solar still by A. E. Kabeel, A. Khalil, Z. M. Omara, M. M. Younes in the paper “Theoretical and experimental parametric study of modified stepped solar still” published in Desalination, Volume 289, 15 Mar. 2012, Pages 12-20. In this work an experimental as well as theoretical investigation was carried out. Two solar stills are used simultaneously and both used saline water; a conventional single sloped solar still and a modified stepped solar still. The influence of depth and width of trays on the performance of the stepped solar still was investigated. The results showed that the productivity of the stepped solar still strongly depended on the tray depth and width. This article does not disclose use of reflectors or side condensers for enhanced productivity. Reference may be made to an article by K. Vinoth Kumar & R. Kasturi Bai entitled “Performance study on solar still with enhanced condensation” published in Desalination, Volume 230, Issues 1-3, 30 Sep. 2008, Pages 51-61. In this article, a basin type solar still (0.5 m2) with improved condensation technique was designed and built, and a performance study was carried out with different samples such as tap water, seawater and dairy industry effluent. The condensation occurred due to the temperature difference on the glass surface and on the four sidewalls, which could be cooled by water circulation through tubes attached on the wall surface for efficiency enhancement. The maximum daily production of the solar still was about 1.4 L/m2·d, and its efficiency was about 30%. The productivity from this still is lower compared to that reported in this patent and also, the use of reflectors is not mentioned.
Reference may be made to an example cited in an article by J. T. Mandi, B. E. Smith & A. O. Sharif, entitled “An experimental wick-type solar still system: Design and construction” published in Desalination, Volume 267, Issues 2-3, 15 Feb. 2011, Pages 233-238. In this work a tilted wick-type solar still was designed and constructed. Charcoal cloth was used as an absorber/evaporator material and for saline water transport. The article does not address general maintenance.